下列叶片的细胞中，不含叶绿体的是（ ）
A：保卫细胞
B：表皮细胞
C：栅栏层细胞
D：海绵层细胞
Children's lives are every time they cross this road in the busy traffic.
—Oh, Dale lost his watch.
选出最恰当的答语（ ）
